1344 Journal of Applied Microscopy 



related to nutrition. In the case of the Protozoa each cell is able to take nutri- 

 ment and carry on respiration over its whole surface. When, however, the cells 

 resulting from the division of a single one remain permanently in contact with 

 one another, it necessarily follows that a smaller portion of each cell can come 

 into contact with and absorb nutriment. Such developmental forms as the 

 blastula and gastrula, and in fact all folds, furrows, invaginations and evagina- 

 tions appearing during development, are explained as the result of the insuffi- 

 cient nourishment which is unable to keep pace with the growth. Since only 

 the cells immediately in contact with nutritive substances are sufficiently nour- 

 ished to support growth, while the cells within and away from nutriment are 

 correspondingly insufficiently nourished, these latter very soon begin to 

 degenerate and show necrobiotic phenomena. 



The author considers that practically all processes of cell differentiation are, 

 from the standpoint of the cell, regressive in nature. The primitive cells or 

 " Blastzellen, " from which are developed all other kinds of cells, are seen in 

 the embryo before any beginning of differentiation, and are characterized by their 

 large size, their richness in cytoplasm, and their large nuclei. Such cells are 

 also found in the adult body in the Malphigian layer of the epidermis, the 

 mucous lining of the alimentary canal, the endothelium of the blood vessels, the 

 germinal epithelium, the osteoblasts, etc. All changes which occur in these 

 "Blastzellen" are regressive in nature. The only progression is found in their 

 viiiJtiplication, which is possible up to a very old age. 



The theory is next applied in detail to the processes of ontogeny and histo- 

 genesis. It is believed that the development of the individual begins with the 

 formation of the ovum within the ovary. The maturation of the ovum marks 

 the beginning of the degenerative changes which ultimately lead to the death of 

 the individual. The egg is left poorer in protoplasm and nuclear material after 

 maturation. The development of the body form in all its details is explained 

 as a result of the better nutritive conditions of cells on the periphery over those 

 in the center of an embryo or an organ. The same principle is applied to the 

 differentiation of the various tissues. Muscle cells or ganglion cells are degen- 

 erated because they have lost the cuboidal or polygonal form of the "Blastzellen" 

 and are less rich in the sort of protoplasm that makes up the body of Amoeba. 

 The chemical as well as the morphological aspect of histogenesis is developed. 



The relation of function to structure and the origin of the functional differen- 

 tiations and adaptations are next discussed. The author is strongly opposed to 

 a teleological consideration of life phenomena and in order to escape some of 

 the difficulties along this line which his theory involves, he advances some 

 astonishing physiological principles. An example will indicate the nature 

 of these. It is stated that the saliva is a product of the regressive met- 

 amorphosis of the poorly nourished cells of the salivary gland, and is useless to 

 the organism. The ptyalin is useless because the sugar into which it converts 

 the starch of the food has to be reconverted into " animal starch. " 



The remainder of the book is devoted to a collection of data relating to the 

 growth in size and weight of the human body and its organs, from birth to old 

 age. These data support the author's view that there is during the course of 



